August 2, 2005Life on Mars? Who knows? Ice on Mars? Most definitelyand now we've got more cold, hard evidence.

On Thursday the European Space Agency released a rare photo of a Martian ice lake in the far northern reaches of the planet. Capping a swirl of dunes at the bottom of a 23-mile-wide (35-kilometer-wide) crater, the frozen lake is thought to exist year-round. The modest temperature and pressure changes in this latitude would not be enough to allow the ice to melt or evaporate.

Water, a key ingredient for life, is believed to have once flowed on Mars, etching the gorges that crisscross the red planet. Today water ice is abundant underground, cakes the poles, and may even form frozen, buried seas (see photo). But it is unusual to find lonely patches of ice away from the poles.

The new image, taken by the agency's Mars Express probe, shows largely true colors. But the depth of the crater's ice-fringed, 1.2-mile-deep (2-kilometer-deep) ridges is exaggerated by a factor of three.